HackerNews MCP Server

Instructions

Implementation Reference

• src/tools/get-user.ts:45-69 (handler)

  The getUserHandler function that executes the tool: validates input with Zod schema, fetches user profile via HNAPIClient, checks existence, validates output, handles errors, and returns MCP CallToolResult.
  export async function getUserHandler(input: unknown): Promise<CallToolResult> { try { // Validate input const validatedParams = GetUserInputSchema.parse(input); // Create API client const client = new HNAPIClient(); // Call users API to get profile const result = await client.getUser(validatedParams.username); // Check if user exists const notFoundError = checkItemExists(result, "User", validatedParams.username); if (notFoundError) { return notFoundError; } // Validate output const validatedResult = GetUserOutputSchema.parse(result); return createSuccessResult(validatedResult); } catch (error) { return handleAPIError(error, "get-user"); } }
• src/tools/get-user.ts:16-22 (schema)

  Zod schema for validating the input parameter 'username' of the get-user tool.
  export const GetUserInputSchema = z.object({ username: z .string() .min(1, "username must not be empty") .regex(/^[a-zA-Z0-9_]+$/, "username must be alphanumeric with underscores only") .describe("HackerNews username"), });
• src/tools/get-user.ts:27-32 (schema)

  Zod schema for validating the output user profile data returned by the HackerNews API.
  export const GetUserOutputSchema = z.object({ username: z.string(), karma: z.number().int().nonnegative(), about: z.string().nullable().optional(), created: z.number().int().positive().optional(), });
• src/tools/get-user.ts:74-111 (registration)

  The getUserTool metadata object defining the tool's name, detailed description, and input schema for MCP server registration.
  export const getUserTool = { name: "get-user", description: `Retrieve public profile information for a HackerNews user. Returns user profile including karma, bio, and account creation date. Use this to: - Check user reputation (karma score) - Read user bio and about information - See when account was created - Verify user existence before searching their content Features: - Username (case-sensitive) - Karma score (total upvotes received) - About/bio text (may contain HTML) - Account creation date (Unix timestamp) Examples: - Get famous user: { "username": "pg" } - Check moderator: { "username": "dang" } - Verify author: { "username": "tptacek" } Username validation: - Alphanumeric characters and underscores only - Case-sensitive - Must exist on HackerNews Returns error if user doesn't exist or username format is invalid.`, inputSchema: { type: "object", properties: { username: { type: "string", description: "HackerNews username (alphanumeric + underscores, e.g., 'pg')", }, }, required: ["username"], }, };
• src/index.ts:45-55 (registration)

  Registration of the get-user tool in the MCP server's listTools handler, including getUserTool in the returned tools array.
  server.setRequestHandler(ListToolsRequestSchema, async () => { return { tools: [ searchPostsToolMetadata, getFrontPageTool, getLatestPostsTool, getItemTool, getUserTool, ], }; });
• src/index.ts:78-80 (registration)

  Dispatch registration in the MCP server's callTool handler switch statement, routing 'get-user' calls to getUserHandler.
  case "get-user": return await getUserHandler(args);